Update forms.py

Author: domdinicola

src/concurrency/forms.py

@@ -1,5 +1,6 @@
 from importlib import import_module
 
+from django.utils import formats
 from django import forms
 from django.core.exceptions import (NON_FIELD_ERRORS, ImproperlyConfigured,
                                     ValidationError,)
@@ -91,7 +92,7 @@ def __repr__(self):
             return ''
 
 
-class VersionField(forms.IntegerField):
+class VersionField(forms.Field):
     widget = HiddenInput  # Default widget to use when rendering this type of Field.
     hidden_widget = HiddenInput  # Default widget to use when rendering this as "hidden".
 
@@ -116,10 +117,12 @@ def prepare_value(self, value):
 
     def to_python(self, value):
         value = super().to_python(value)
+        if value in self.empty_values:
+            return 0
         try:
-            return int(self._signer.unsign(value))
-        except BadSignature:
-            raise VersionError(f'Bad signature: {value}')
+            return int(self._signer.unsign(str(value)))
+        except (BadSignature, ValueError):
+            raise VersionError(value)
 
     def widget_attrs(self, widget):
         return {}